Power transmission networks are around us every day. The most common is the alternating current (AC) power network within our homes and office buildings. The utility companies use this wired network to supply AC power to us. This network is capable of supplying large amounts of power to a device directly connected to it.
The key to the operation of this network is the direct connection. It is not always possible or practical to hardwire or plug-in every device. An example of this can be seen by examining the building automation market.
There is currently a drive to conserve energy in office buildings and homes. This is done by optimizing how the power is used. As an example, there is no need to light a room when it is not occupied. This problem has been addressed and is solved by placing a motion sensor in the room. When there is no motion for a given period of time, the lights are turned off.
The problem with this solution is that each motion sensor requires power. This means that each sensor is hardwired to the AC power network or must contain a battery. This may not be practical in all applications. Each sensor must also have a way to control the operation of the lights in the room.
The current trend is to implement wireless sensors. However, the term “wireless” in this case refers only to the communication portion of the device. The power for the device must still be derived from the traditional sources such as the AC power network or batteries.